light pen 
noun
1A handheld pen-like photosensitive device held to the display screen of a computer terminal for passing information to the computer.You may have to adjust the brightness of your monitor to get your light pen to work properly....
- Various other light pens have been developed which include a lens for focusing the axially received light.
- The radiated light is directed so as to be projected from a tip of the light pen as required.
2A handheld light-emitting device used for reading barcodes.
- kick something off
- kicksorter
- kickstand
- kick-start
- kick-starter
- kick the bucket
- kick the can down the road
- kick the shit out of
- kick the tin
- kick-to-kick
- kick-turn
- kick up
- kick up (a) dust
- kick up a fuss (or a stink)
- kick up one's heels
- kicky
- kid
- kid brother
- kidder
- Kidderminster
- Kidderminster carpet
- kiddie
- kiddie porn
- kiddies' pool
- kiddies pool